1. Field of the Invention
The present invention relates to monitoring patterns for detecting a defect in a semiconductor circuit and methods for detecting the defect. More particularly, the present invention relates to monitoring patterns for detecting a defect by electron beam scanning and method for detecting the defect.
2. Description of the Related Art
Voltage contrast inspection has been used to monitor semiconductor circuits and processes. The voltage contrast inspection may utilize the intensity of secondary electrons, released when a test pattern is exposed to electron beam, which may be represented as a voltage contrast image.
In a test pattern, a low potential state portion may be a high intensity portion of secondary electrons, while a high potential state portion may be a low intensity portion thereof. The low potential state portion may thus be brightly displayed, while the high potential state portion may be darkly displayed.
During a typical voltage contrast inspection, the low potential state portion may be designated as a grounded pattern, and the high potential state portion may be designated as a floating pattern. When defects are generated in the test pattern to cut off the grounded pattern or to connect the grounded pattern to the floating pattern, a portion cut off from the grounded pattern may be displayed as the high potential state portion, and the floating pattern short-circuited from an adjacent grounded pattern may be displayed as the low potential state portion. Accordingly, when the portion displayed on a voltage contrast image is different from the portion displayed by scanning the test pattern with an electron beam, it may be employed as a detection method to judge the type and location of the defect.
FIG. 1 illustrates an intensity graph of a test pattern for detecting a defect and a voltage contrast image. The test pattern may be made of a conductor in which grounded patterns 10 and floating patterns 12 are alternately formed. During a voltage contrast inspection, the grounded patterns 10 may be displayed as a bright image and the floating patterns 12 may be displayed as a dark image. The test pattern may be scanned using an electron microscope in an X-direction, and secondary electrons may be detected by a secondary electron detector to obtain the voltage contrast image including the bright grounded pattern 10 and the dark floating pattern 12.
The intensity of secondary electrons may be represented as a graph 14 by scanning the test pattern in the X-direction. When a defect, e.g., a short-circuit or an open-circuit, occurs in the test pattern, higher values and lower values may be alternately displayed on the graph 14.
As illustrated in FIG. 2, when a short-circuit Ax or an open-circuit Ay occurs in a circuit being tested, an intensity value displayed on the graph 14 may be different from an expectation value. For example, when a voltage contrast inspection value is obtained while scanning the test pattern in the X-direction, an intensity value at a position where the short-circuit Ax occurs in the grounded pattern 10a may be smaller than an expectation value Ex. Similarly, an intensity value of a position where the open-circuit Ay occurs in a floating pattern 12a may be larger than an expectation value Ey. The position of the defect may be detected by the scanning the test pattern with the X-direction scan and an Y-direction scan.
The voltage contrast inspection may thus be conducted to detect the position of the defect occurring in the test pattern, as well as the type of the defect. The voltage contrast inspection may therefore be advantageous to monitor a pattern and a process on a substrate inside a production line. Nonetheless, the voltage contrast inspection may be incapable of judging whether the defect detected by the voltage contrast inspection is an electrical defect causing a malfunction of a semiconductor device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.